Chapter 3: Problem 13
For the following exercises, find the average rate of change of each function on the interval specified for real numbers \(b\) or \(h\) in simplest form. $$ j(x)=3 x^{3} \text { on }[1,1+h] $$
Short Answer
Expert verified
The average rate of change is \(9 + 9h + 3h^2\).
Step by step solution
01
Understand the formula for average rate of change
The average rate of change of a function \(j(x)\) from \(x=a\) to \(x=b\) is given by the formula: \[ \frac{j(b) - j(a)}{b-a} \] . We are asked to find the average rate of change of the function \(j(x) = 3x^3\) from \(x=1\) to \(x=1+h\).
02
Evaluate the function at the endpoints of the interval
Compute \(j(1)\) and \(j(1+h)\) using the function definition. - \(j(1) = 3(1)^3 = 3\) - \(j(1+h) = 3(1+h)^3 = 3(1 + 3h + 3h^2 + h^3) = 3 + 9h + 9h^2 + 3h^3\).
03
Substitute into the average rate of change formula
Substitute the values from Step 2 into the average rate of change formula and perform the subtraction:\[\frac{3 + 9h + 9h^2 + 3h^3 - 3}{(1+h) - 1} = \frac{9h + 9h^2 + 3h^3}{h}\].
04
Simplify the expression
Cancel \(h\) in the numerator and denominator in the expression:\[9 + 9h + 3h^2 \]. So, the average rate of change is \(9 + 9h + 3h^2\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Functions
Functions are critical building blocks in mathematics. A function is like a machine where you input a number, it processes it, and outputs another number. Essentially, a function describes a relationship between two sets of numbers. In our example, the function is expressed as \( j(x) = 3x^3 \). Here, \( x \) is the input, and \( j(x) \) - or occasionally denoted as the output - is the result after applying the function on \( x \). Functions behave consistently based on their definitions. For instance, at \( x = 1 \), we simply replace \( x \) with \( 1 \) in \( 3x^3 \) and get 3. This same substitution principle applies at any point along the interval.When dealing with functions, it is important to understand:
- How the inputs and outputs are related.
- What happens to the function when the input changes slightly, which directly ties into the average rate of change concept.
Calculus
Calculus is a branch of mathematics focused on change. One of its core ideas is understanding how things change and accumulate over time or space. The average rate of change is a fundamental concept in calculus. Imagine tracking how a plant grows over a week. The average rate of change calculates how much the plant's height increased divided by the duration it took. For functions like \( j(x) = 3x^3 \), we look at how the output value \( j(x) \) changes as we adjust \( x \) from \( 1 \) to \( 1 + h \).With calculus, you learn to:
- See how functions behave as inputs change, emphasizing growth and decay.
- Determine how these changes accumulate over particular intervals.
Polynomials
Polynomials are a type of mathematical expression that are made up of variables raised to whole numbers (like \(x^3\)), coefficients (like \(3\)), and the operation of addition. They can appear simple, like \( j(x) = 3x^3 \), or far more complex with multiple terms and higher degrees.Working with polynomials involves understanding a few basics:
- Each term in a polynomial consists of a coefficient and a degree, which is the power to which the variable is raised.
- They are heavily utilized in calculus since they are easy to manipulate and differentiate.